In a large bowl, stir together the bread flour, whole wheat flour, yeast and 2 1/4 cups of the warm water using a fork or your hands. Mix until a shaggy dough forms and all of the dry flour has been incorporated. Cover the bowl with a clean towel and let stand at room temperature for 20 minutes.

Sprinkle the salt and pour the remaining 1/4 cup of the water over the dough. Using your hands, squeeze and knead the dough until the salt and water are all incorporated and the dough forms a ball. Cover with a clean towel and let stand at room temperature for 20 minutes.

Stretch and fold the dough over itself in the bowl four times, rotating the bowl a quarter turn with each fold and using wet hands to prevent the dough from sticking. Cover and let stand for 20 minutes. Repeat the folding process four more times, for a total of five folds over 1 hour and 20 minutes.

Turn the dough out onto a heavily floured surface, handling as little as possible to keep it bubbly. Dust the top of the dough heavily with flour.

Cut the dough in half lengthwise using a bench scraper or large knife. Gently stretch each dough piece into an about 12-by-4-inch rectangle and transfer to a parchment-lined, unrimmed baking sheet. Cover with a clean dish towel and let rise at room temperature until puffy and increased in volume, 45 minutes to 1 hour 15 minutes.

About 30 minutes before the dough is finished proofing, preheat the oven to 475° with a baking stone or inverted baking sheet on the center rack. Slide the parchment paper with the dough onto the preheated baking stone.

Bake until the loaves are golden brown, 18 to 22 minutes. Transfer the loaves to a wire rack to cool. Serve warm or at room temperature.